Easily transportable devices with wireless telecommunications capabilities, such as mobile telephones, personal digital assistants, handheld computers, and similar devices, will be referred to herein as user equipment (UE). A communications connection between two UEs can be referred to as a call or a session.
As telecommunications technology has evolved, more advanced equipment has been introduced that can provide services that were not possible previously. This advanced equipment might include, for example, an Enhanced Node B (ENB) rather than a base station or other systems and devices that are more highly evolved than the equivalent equipment in a traditional wireless telecommunications system. Such advanced or next generation equipment may be referred to herein as long-term evolution (LTE) equipment.
In traditional wireless telecommunications systems, transmission equipment in a base station transmits signals throughout a geographic region known as a cell. For LTE and other advanced equipment, the region in which a UE can gain access to a telecommunications network might be referred to by a different name, such as a hot spot. The term “cell” will be used herein to refer to any region in which a UE can gain access to a telecommunications network, regardless of the type of UE and regardless of whether the region is a traditional cell, a region served by LTE equipment such as an ENB, or some other region or location in which wireless telecommunications services are available.
Different UEs might use different types of radio access technology (RAT) to access a telecommunications network. Some UEs, which can be referred to as multi-domain UEs or multi-mode UEs, are capable of communicating using more than one RAT. For example, multi-mode UEs may include UEs that can obtain service from at least one mode of UMTS (Universal Mobile Telecommunications System), and one or more different systems such as GSM (Global System for Mobile Communications) bands or other radio systems. As defined herein, multi-mode UEs may be of any various type of multi-mode UE as defined or provided in 3GPP (3rd Generation Partnership Project), Technical Specification Group (TSG) Terminals, Multi-Mode UE Issues, Categories, Principles, and Procedures (3G TR 21.910), which is incorporated herein by reference for all purposes. Often examples of RATs or of network technologies that might use different types of RATs include Code Division Multiple Access (CDMA2000), UTRAN (UTMS Terrestrial Radio Access Network), GSM, GSM EDGE Radio Access Network (GERAN), Generic Access Network (GAN), Wireless Fidelity (WiFi), Wireless Local Area Network (WLAN), General Packet Radio Service (GPRS), Worldwide Interoperability for Microwave Access (WiMAX), 1× Evolution-Data Optimized (1× EV-DO), High-Speed Downlink Packet Access (HSDPA), Digital Enhanced Cordless Technology (DECT), and High Rate Packet Data (HRPD). Other RATs or other network technologies based on these RATs may be familiar to one of skill in the art.
Some technologies, such as GSM and CDMA, may be publicly licensed and regulated and serve cells that cover large geographic areas. Such technologies will be referred to herein as macrotechnologies and the cells that they serve will be referred to as macrocells. Other technologies, such as WiFi and home enhanced node B, may be privately managed and serve cells that cover small spaces such as homes, businesses, or limited publicly accessible areas. Such technologies will be referred to herein as microtechnologies and the cells that they serve will be referred to as microcells.